This comprehensive monograph investigates the computational power of Turing machines with sublogarithmic space. The studies are devoted to the Turing machine model introduced by Stearns, Hartmanis, and Lewis (1965) with a two-way read-only input tape and a separate two-way read-write work tape. The book presents the key results on space complexity, also as regards the classes of languages acceptable, under the perspective of a sublogarithmic number of cells used during computation. It originates from courses given by the author at the Technical University of Gdansk and Gdansk University in...